Magnetic Properties and Microstructure Studies of Hot-Deformed Nd-Fe-B Magnets With Zr Addition

We synthesized bulk isotropic and anisotropic Nd_13.5Fe_77.5Co₃B₆ and Nd_13.5Fe_76.5Co₃Zr₁B₆ magnets by spark plasma sintering (SPS). For hot-pressed magnets, the values of remanence (B_r) and coercivity (H_ci) decreased with addition of Zr. After hot-deformation, it was difficult to obtain the desired alignment for Nd_13.5Fe_76.5Co₃Zr₁B₆ magnets, which had a lower degree of texture compared with Nd_13.5Fe_77.5Co₃B₆ even at a higher than 65% deformation ratio. The research on the microstructure of hot-pressed and hot-deformed magnets shows that Zr addition made the grain finer for hot-pressed magnets and after hot-deforming there were still plenty of areas of poor texture where the content of Zr was higher than 1 at% according to the results of energy-dispersive spectroscopy. It reveals that Zr addition could retard the grain growth and the development of texture during hot-pressing and hot-deforming.